JP4591760B2 - Electric discharge machining apparatus and electric discharge machining method - Google Patents

Description

  The present invention relates to an electric discharge machining apparatus and an electric discharge machining method for providing a hole having a predetermined shape penetrating a workpiece by electrode discharge.

2. Description of the Related Art Conventionally, a wire electric discharge machine is known as an apparatus for providing a hole having a predetermined shape penetrating a conductor (for example, metal) that is a workpiece. This wire electrical discharge machining apparatus provides a relative feed between the workpieces while repeatedly generating an electric discharge pulse in a state where a machining fluid is supplied to a machining gap between wire electrodes opposed to the workpiece. It is an apparatus which provides the hole of the predetermined shape penetrated in.
In this wire electric discharge machining apparatus, a camera is attached above the workpiece, the machining site is photographed with this camera, the photographed information is transmitted to the image processing apparatus, and binarization processing is performed. Some control the relative position of the workpiece and the electrode based on the above. (See Patent Document 1 below). According to this wire electric discharge machining apparatus, a machining site is imaged with a camera, this is binarized, the relative position between the workpiece and the electrode is controlled based on the processed information, and the machining is performed again. By repeating this process until the measured value of the shape matches the target value, it can be finished to a predetermined shape (dimension).
In addition, since measurement by such image processing is performed based on the brightness of an image, it is necessary to irradiate the processing site to be photographed with light. Conventionally, an electric discharge machining apparatus in which an illumination device for irradiating this light is provided on the camera side is also known (see Patent Document 2 below). According to this electric discharge machining apparatus, the surface of the workpiece is obtained by irradiating the workpiece with light from the illumination device and obtaining an image of the light (reflected light) reflected by the surface of the workpiece by the image processing apparatus. Accurate machining can be performed by adjusting while observing the machining state.
Japanese Patent No. 2876032 JP-A-11-104919

By the way, since electric discharge machining is performed while repeatedly generating an electric discharge pulse in a state where the machining liquid is supplied to the gap between the workpiece and the electrode, the workpiece is usually machined while being immersed in the machining liquid. For this reason, in both Patent Documents 1 and 2, the camera and the illumination device for obtaining an image are arranged above the workpiece so as not to be immersed in the processing liquid. As a result, the illumination method for obtaining an image with the camera is limited to the reflective illumination that emits light from the same direction as the camera.
In the image recognition method using the reflected illumination, depending on the state of the edge portion formed by wire electric discharge machining, the light from the illumination device and the light from the illumination device strike and reflect the inner surface of the hole formed by the machining. May interfere with each other and cause interference fringes on the inner surface of the hole. When this interference fringe is generated, a high brightness portion and a low brightness portion are generated in the vicinity of the edge portion of the hole, and there is a problem that the edge portion cannot be accurately recognized in image processing.
Further, there are usually fine irregularities of processing marks and scratches generally called “surface roughness” on the surface of the workpiece. Because the unevenness can make a difference in the amount of reflected light, the brightness of the concave portion of the processing trace is lowered, and the edge portion cannot be accurately recognized due to the influence of the low brightness portion in the vicinity of the edge portion in image processing. is there.
Thus, the image information obtained by the reflected illumination includes a noise component which becomes a problem when the formed shape is accurately obtained.
Therefore, conventionally, the image information obtained by the reflected illumination is binarized by the image processing apparatus to eliminate these influences. However, since the binarization process converts the original image information into black and white information according to the set threshold, the image information is compressed, and the measurement result varies greatly depending on the surface state of the workpiece. The image processing method is unavoidable for dimensional measurement such that the measurement result varies greatly depending on the set threshold value.

  In view of the above circumstances, the present invention provides an electric discharge machining apparatus and an electric discharge machining method capable of machining a workpiece with high accuracy based on accurate information on the shape of a hole formed in the workpiece. The purpose is to do.

The invention according to claim 1 is opposite to the imaging means, the processing means for providing a hole having a predetermined shape penetrating the workpiece, the imaging means for imaging the workpiece, and the imaging means through the workpiece. An illuminating unit provided on the side for irradiating the workpiece with light, an image processing unit for processing image information captured by the imaging unit, and the workpiece based on the information processed by the image processing unit and control means for controlling the relative position of the processing means and the edge portion of the hole of the object to be processed by chromatic and air cleaning device for blowing an air flow, wherein the workpiece is immersed in machining fluid In this state, the processing means processes the shape of the hole of the workpiece, and the air cleaning device applies the air flow to the edge portion of the hole of the workpiece drawn out from the processing liquid. By spraying The discharge machining apparatus for removing the working fluid adhering to the parts, the processing means is a wire electrode for machining the shape of the hole by discharge pulses occurring between the holes, the wire electrode Is provided so as to be movable in the horizontal direction penetrating the hole in the machining liquid, and the imaging means and the illumination means are a straight line that is outside the machining liquid and connects the imaging means and the illumination means. Is arranged so as to be parallel to the moving direction of the wire electrode, and the workpiece is between a straight line connecting the imaging means and the illumination means, and in the machining liquid. It is provided to be movable .

According to invention of Claim 1, light is irradiated to a to-be-processed body from an illumination means. When the workpiece is irradiated with light, the workpiece is imaged by the imaging means using the transmitted light that has passed through the workpiece. Based on the image information picked up by the image pickup means, the image processing means performs image processing such as grayscale processing or binarization processing. Based on the image information processed by the image processing means, the workpiece or the processing means is moved by the control means, the relative position between the workpiece and the processing means is controlled, and the workpiece is processed.
Here, since the illumination unit is provided on the side opposite to the imaging unit via the workpiece, the luminance of the transmitted light that passes through the hole formed in the workpiece is increased, and the workpiece The difference from the brightness of the transmitted light in other parts increases. As a result, the image processing in the image processing unit can be easily performed and the processing accuracy can be increased, so that the processing accuracy of the workpiece can be improved. In particular, since the difference in brightness can be clarified, it is possible to accurately recognize the edge portion of the hole formed in the workpiece that could not be accurately recognized in the past, and to the workpiece. Even if there is a scratch, it will not be mistakenly recognized as an edge portion of the hole.

According to a second aspect of the invention, the electric discharge machining apparatus according to claim 1, said illuminating means, the imaging means, and the hole is characterized by being located on the same straight line at the time of measurement.

According to the second aspect of the present invention, the illumination unit, the imaging unit, and the hole formed in the workpiece are positioned on the same straight line at the time of measurement, so that the light emitted from the illumination unit is processed. It can be easily transmitted through the hole formed in the body. As a result, an image having no edge shadow in any direction can be obtained even on a thick workpiece, and the edge portion of a hole formed in the workpiece can be accurately recognized.

According to a third aspect of the present invention, there is provided a light irradiating step of irradiating light from the illumination unit disposed on the opposite side of the imaging unit through the workpiece to the workpiece, and the imaging unit. An image processing step for image processing the image information of the workpiece using transmitted light that passes through the workpiece, and a processing step for forming a hole having a predetermined shape penetrating the workpiece by a processing means. A control step of controlling a relative position between the workpiece and the processing means based on the image-processed information; and an air cleaning device for an edge portion of the hole of the workpiece. An air cleaning step of blowing an air flow, and in the processing step, the shape of the hole of the workpiece is processed by the processing means in a state where the workpiece is immersed in a processing liquid, In the air cleaning process, The machining liquid adhering to the edge portion is removed by blowing the air flow from the air cleaning device to the edge portion of the hole of the workpiece drawn from the inside of the machining fluid. In the electric discharge machining method, the machining means is a wire electrode for machining the shape of the hole by an electric discharge pulse generated between the hole and the wire electrode penetrates the hole in the machining liquid. The imaging unit and the illuminating unit are provided so as to be movable in a horizontal direction, and the straight line connecting the imaging unit and the illuminating unit is parallel to the moving direction of the wire electrode. The workpiece is provided so as to be movable between a straight line connecting the imaging means and the illumination means and in the machining liquid. .

According to invention of Claim 3 , in a light irradiation process, light is irradiated toward a to-be-processed body from the illumination means arrange | positioned on the opposite side to an imaging means through a to-be-processed body. In the image processing step, the image information of the workpiece imaged by the imaging means is subjected to image processing using transmitted light that passes through the workpiece. Based on the image-processed information, the control unit controls the relative position between the workpiece and the processing unit. In the processing step, a hole having a predetermined shape penetrating the workpiece is formed by the processing means. Here, since the illumination unit is provided on the side opposite to the imaging unit via the workpiece, the luminance of the transmitted light that passes through the hole formed in the workpiece is increased, and the workpiece The difference from the brightness of the transmitted light in other parts increases. As a result, the image processing in the image processing unit can be easily performed and the processing accuracy can be increased, so that the processing accuracy of the workpiece can be improved. In particular, since the difference in brightness can be clarified, it is possible to accurately recognize the edge portion of the hole formed in the workpiece that could not be accurately recognized in the past, and to the workpiece. Even if there is a scratch, it will not be mistakenly recognized as an edge portion of the hole.

According to a fourth aspect of the present invention, in the electric discharge machining method according to the third aspect , in the light irradiation step, light is irradiated from the illuminating unit located on the same straight line as the imaging unit and the hole. It is characterized by that.

According to the fourth aspect of the present invention, in the light irradiation step, light is irradiated from the illumination unit located on the same straight line as the imaging unit and the hole. It is possible to make it easy to permeate through the hole formed in the. As a result, an image having no edge shadow in any direction can be obtained even on a thick workpiece, and the edge portion of a hole formed in the workpiece can be accurately recognized.

  ADVANTAGE OF THE INVENTION According to this invention, a to-be-processed body can be processed with high precision based on the exact information regarding the shape of the hole formed in the to-be-processed body.

  Next, a wire electric discharge machining apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the wire electric discharge machining apparatus 10 is configured to send the wire electrode 42 in the lateral direction, and includes an XY table 12 to which a metal plate M as a workpiece is attached. . The XY table 12 is provided so as to be movable in the X-axis direction and the Y-axis direction, and the movement is controlled by the control device 24.

  Further, on the first surface MF side (Z-axis 46 side) of the metal plate M attached to the XY table 12, an imaging device (imaging means) 14 is disposed at a position where it is not immersed in the processing liquid during processing. The imaging device 14 is placed on a camera table 16 attached to a Z axis 46 that is movable in the Z axis direction. The movement of the camera table 16 in the Z-axis direction is controlled by the control device 24. Thereby, even when the thickness of the metal plate M to be processed changes, it is possible to move the position of the imaging device 14 to a position corresponding to the thickness by the control device 24 and to correspond to the thickness of the metal plate M. be able to.

Further, an illumination device (illuminating means) 18 for irradiating the second surface MB side of the metal plate M with light on the second surface MB side (UV shaft 47 side) of the metal plate M attached to the XY table 12. Is installed on the illumination table 20 at a position facing the imaging device 14.
Thus, in the wire electric discharge machining apparatus 10 of this embodiment, the illumination device 18 is provided on the opposite side of the imaging device 14 via the metal plate M at the time of measurement. More specifically, the illumination device 18, the imaging device 14, and the hole 22 formed in the metal plate M are located on the same straight line at the measurement position so as not to be immersed in the processing liquid during processing. It is configured.

  Further, the wire electric discharge machining apparatus 10 includes a control device (control means) 24. The control device 24 controls the machining operation by moving the XY table 12, the machining operation based on the measurement result, and the operation of the measurement control device 26.

  As shown in FIG. 2, the wire electric discharge machining apparatus 10 includes a measurement control device 26. The measurement control device 26 operates in accordance with various commands from the control device 24, and receives image information captured by the cleaning device control unit 50, the illumination device control unit 48, and the imaging device 14 as a predetermined signal. Unit 28, an image processing unit (image processing means) 30 that performs edge detection by grayscale processing based on a signal input by image input unit 28, a measurement unit 32 that measures a shape from the detected edge, Comparison / determination of measurement result and machining target value, discrimination of continuation / stop of machining, selection of machining conditions according to machining state, comparison / machining condition selection unit 34, each control program, machining target value And a storage unit 36 for storing processing conditions and the like.

Moreover, in the wire electric discharge machining apparatus 10 of this embodiment, the hole 22 of the metal plate M is machined so as to have a predetermined shape inside the machining liquid L stored in the machining tank 40. For this reason, the processing liquid cleaning device 38 for cleaning the hole 22 processed in the metal plate M after processing is disposed on the UV shaft 47 side of the wire guide 45, and the air cleaning device 39 is disposed on the Z axis 46 side of the wire guide 45. Has been. The machining liquid cleaning mechanism 38 injects the machining liquid L into the machining portion of the metal plate M in the machining liquid L, and can remove the machining waste adhering to the machining surface.
After the machining waste is removed, the metal tank M is drawn out of the machining liquid L by lowering the machining tank 40, and then air is blown onto the metal plate M by blowing air to the holes 22 processed into the metal plate M by the air cleaning mechanism 39. The attached machining liquid L can be removed.

  Next, a wire electric discharge machining method using the wire electric discharge machining apparatus of the present embodiment will be described.

  As shown in FIGS. 1 to 3, a metal plate M as a workpiece is attached to the XY table 12.

  Next, the XY table 12 is moved to an automatic connection position (not shown) according to a command from the control device 24, and the wire electrode 42 is passed through the fine hole 22 formed in advance in the metal plate M. After the wire electrode 42 is passed through the metal plate M, the XY table 12 moves together with the wire electrode 42 guided by the guide roller 44, and the wire electrode 42 is positioned on the wire guide 45.

  Here, the wire electrode 42 is positioned on the wire guide 45 via the guide roller 44, and a constant tension is always applied to the wire electrode 42. The wire electrode 42 is connected to a processing power source (not shown) so that a predetermined voltage is applied.

  When the wire electrode 42 is positioned by the wire guide 45, the processing tank is raised by a command from the control device 24, and the processing position of the metal plate M attached to the XY table 12 is immersed in the processing liquid L. When the metal plate M is immersed in the machining liquid L, in this state, a voltage is applied to the wire electrode 42 from a machining power source (not shown) according to a command from the control device 24. When a voltage is applied to the wire electrode 42, a discharge pulse is generated between the wire electrode 42 and the hole 22 of the metal plate M, and the movement of the XY table 12 is controlled by the control device 24 based on the control program. The shape of the hole 22 programmed in advance in the plate M is processed (step 100).

  When the processing of the shape of the hole 22 formed in the metal plate M is completed, the wire electrode 42 is cut by a wire electrode cutting mechanism (not shown) according to a command from the control device 24 and is collected in a wire electrode collection box (not shown) on the wire electrode discharge side. The Next, the following cleaning operation is performed according to a command from the control device 24. That is, the hole 22 of the metal plate M is moved to the position of the machining liquid cleaning device 38 in a state where the hole 22 is immersed in the machining liquid, and the machining liquid L is injected from the machining liquid cleaning device 38 onto the metal plate M. Thereby, the processing waste adhering to the processing surface of the hole 22 of the metal plate M can be removed. As a result, it is possible to improve the measurement accuracy without being affected by machining waste when the imaging device 14 images the hole 22 of the metal plate M.

  Next, after the processing tank is lowered and the metal plate M is drawn out of the processing liquid L, the hole 22 of the metal plate M is moved to the position of the air cleaning device 39, and the cleaning device controller 50 of the measurement control device 26 An air flow is blown from the air cleaning device 39 whose operation is controlled to the edge portion of the hole 22 of the metal plate M (step 120). Thereby, the machining liquid L adhering to the edge portion can be removed, and the measurement accuracy is improved without being affected by the machining liquid L when the imaging device 14 images the hole 22 of the metal plate M. Can do.

  When the cleaning operation is completed, the illumination device 18 is controlled by the illumination device control unit 48 of the measurement control device 26, and light is emitted from the illumination device 18.

  Next, the XY table 12 is controlled by the control device 24, and the XY table 12 moves to a position where the illumination device 18, the imaging device 14, and the hole 22 of the metal plate M are aligned.

  Next, the Z-axis 46 is controlled by the control device 24, and the camera table 16 is moved in the Z-axis direction so as to match the focal position of the imaging device 14.

  When the focal position of the imaging device 14 is matched, the imaging device 14 is controlled by the control device 24, and the part of the hole 22 of the metal plate M is imaged. At this time, the light emitted from the illuminating device 18 passes through the hole 22 formed in the metal plate M, and the solid portion without the hole does not transmit light, so that the hole-shaped light formed is incident on the imaging device 14. To do. As described above, in the imaging device 14, the processed portion (the hole 22 and the vicinity thereof) is imaged using the transmitted light (step 140).

  When the shape of the hole 22 of the metal plate M is larger than the field of view of the imaging device 14, the control device 24 moves the XY table 12 in the X axis direction and the Y axis direction so that the shape of the hole is within the field of view of the imaging device 14. And at least two or more locations are imaged by the imaging device 14.

  Image information captured by the imaging device 14 is transmitted to the image input unit 28. The image information transmitted to the image input unit 28 is subjected to edge detection by gradation processing in the image processing unit 30 (step 160). In other words, the shading process in the image processing unit 30 means that an image is captured by shading brightness data in units of pixels, and edge detection is performed based on differential data of brightness values, so that the resolution (sub-pixel) is higher than the pixels of the imaging device. This is a technique for performing high-accuracy edge detection at, and the finishing degree of processing of the hole 22 is determined from the shading information of the image.

  Here, since the illuminating device 18 is provided on the opposite side to the imaging device 14 via the metal plate M, the amount of light transmitted through the hole 22 of the metal plate M and the substantial part of the metal plate M that does not transmit light. And the difference in brightness between the portion of the hole 22 and the substantial part of the metal plate M increases. For this reason, the edge detection by the shading process in the image processing unit 30 can be easily performed, and the processing accuracy can be improved.

  Next, the dimension (shape) of the hole 22 of the metal plate M is measured by the measurement unit 32 based on the edge position detected by the density processing in the image processing unit 30 and the imaging position information transmitted from the control device 24. (Step 180).

  Based on the measurement result, the comparison determination / machining condition selection unit 34 compares the machining target value stored in the storage unit 36 with the dimension (shape) of the hole 22 of the metal plate M to the machining target dimension (shape). It is determined whether or not (step 200).

  Next, if the size (shape) of the hole 22 of the metal plate M is determined to be within the target size (shape) by the comparison determination / processing condition selection unit 34, it is determined whether the hole 22 of the metal plate M is after finishing cutting. (Step 220) If it is after finishing cut, processing is stopped (Step 240), and the hole 22 of this metal plate M is handled as a non-defective product.

  On the other hand, if it is not after the finish cut, the processing is stopped (step 260), and since the processed surface roughness is not finished, the hole 22 of the metal plate M is handled as a defective product.

  Next, when the comparison determination / processing condition selection unit 34 determines in step 200 that the dimension (shape) of the hole 22 of the metal plate M is not within the target dimension (shape), the comparison determination / processing condition selection unit 34 It is determined whether or not there is a machining allowance for the hole 22 in the metal plate M (step 280). When the comparison determination / processing condition selection unit 34 determines that there is no machining allowance for the hole 22 in the metal plate M, the machining is stopped ( Step 300), the metal plate M is handled as a defective product.

  On the other hand, if it is determined by the comparison / working condition selection unit 34 that there is a machining allowance for the hole 22 of the metal plate M, it is determined whether the hole 22 of the metal plate M has been finished cut (step 320). If it is determined that the finish cutting has been performed, the optimum additional machining condition among the additional machining conditions stored in the storage unit 36 is selected by the comparison determination / processing condition selection unit 34 (step 340).

When the optimum additional machining conditions are selected by the comparison determination / machining condition selection unit 34,
The selected machining conditions are transmitted to the control device 24, and additional processing is performed on the holes 22 of the metal plate M under the control of the control device 24 under the transmitted machining conditions. (Step 360)

  On the other hand, if it is determined in step 320 that the hole 22 of the metal plate M is not after finishing cutting by the comparison determination / processing condition selection unit 34, the next processing cost corresponding to the cutting process stored in the storage unit 36 is stored. The optimum machining conditions for the cutting process are selected by the comparison determination / machining condition selection unit 34 (step 380). When an optimum machining condition for the next cutting process is selected by the comparison determination / machining condition selection unit 34, the selected machining condition is transmitted to the control device 24. The next cutting process is performed on the hole 22 of the metal plate M under the control of the control device 24 under the transmitted processing conditions. (Step 100)

  Thereafter, the steps after step 120 are repeated until the dimension (shape) of the hole 22 of the metal plate M is within the machining target value.

  In this way, processing of the metal plate M, cleaning of the metal plate M, measurement of the processed portion of the metal plate M, pass / fail determination, confirmation of processing cost, determination of processing continuation / stop, selection of optimum additional processing conditions, additional processing, Selection of optimum machining conditions for the next cutting process according to the machining allowance, and machining under the machining conditions according to the machining allowance can be performed automatically, and unmanned operation can be realized.

  As described above, according to the wire electrical discharge machining apparatus 10 and the wire electrical discharge machining method of the present embodiment, the illumination device 18 is disposed on the opposite side of the imaging device 14 with the metal plate M interposed therebetween. The difference between the luminance of the light transmitted through the hole 22 formed in the metal plate and the luminance of the solid portion of the metal plate M without the hole is increased. As a result, it is possible to easily perform edge detection by shading processing in the image processing unit 30 and to improve processing accuracy, so that the edge portion can be accurately recognized. Thereby, since it can process based on the measurement result of an exact dimension (shape), the processing precision of the metal plate M can be raised.

  In particular, since the illumination device 18, the imaging device 14, and the hole 22 formed in the metal plate M are located on the same straight line during measurement, the light emitted from the illumination device 18 is formed in the metal plate M. It is possible to facilitate the permeation of the holes 22. As a result, an image having no shadow is obtained at the edges in all directions even on a thick workpiece, and the edge portion of the shape formed on the workpiece can be accurately recognized.

  In the above-described embodiment, the configuration in which the control device 24 controls the movement of the XY table to position the metal plate M is shown. However, the configuration is not limited to this configuration. For example, the position of the wire electrode 42 is controlled by the control device. You may comprise so that it may control and position by 24.

It is explanatory drawing which shows the process by the electric discharge machining apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the electric discharge machining apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the process by the electric discharge machining apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

10 Wire electrical discharge machining equipment (electrical discharge machining equipment)
14 Imaging device (imaging means)
18 Illumination device (illumination means)
24 Control device (control means)
30 Image processing unit (image processing means)
42 Wire electrode (processing means)
M metal plate (workpiece)

Claims (4)

Processing means for providing a hole having a predetermined shape penetrating the workpiece, imaging means for imaging the workpiece, and provided on the opposite side to the imaging means via the workpiece. Illuminating means for irradiating light, image processing means for processing image information picked up by the image pickup means, and a relative position between the workpiece and the processing means based on information processed by the image processing means. and control means for controlling, and a air cleaning apparatus which blows an air flow to the edges of the hole in the workpiece possess,
In a state where the workpiece is immersed in a machining fluid, the machining means processes the shape of the hole of the workpiece, and an edge portion of the hole of the workpiece drawn from the inside of the machining fluid In contrast, the air cleaning device blows the air flow to remove the machining liquid adhering to the edge portion ,
The processing means is a wire electrode that processes the shape of the hole by a discharge pulse generated between the hole and the hole,
The wire electrode is provided movably in the horizontal direction penetrating the hole in the machining liquid,
The imaging means and the illuminating means are arranged outside the working fluid and so that a straight line connecting the imaging means and the illuminating means is parallel to the moving direction of the wire electrode,
The electric discharge machining apparatus , wherein the workpiece is provided so as to be movable between a straight line connecting the imaging unit and the illumination unit and in the machining liquid . The electric discharge machining apparatus according to claim 1, wherein the illumination unit, the imaging unit, and the hole are positioned on the same straight line during measurement . A light irradiation step of irradiating light from the illumination means arranged on the side opposite to the imaging means through the workpiece toward the workpiece;
An image processing step of performing image processing on image information of the workpiece imaged by the imaging means using transmitted light that passes through the workpiece;
A processing step of forming a hole having a predetermined shape penetrating the workpiece by a processing means;
A control step of controlling a relative position between the workpiece and the processing means by a control means based on the image processed information;
An air cleaning step of blowing an air flow with an air cleaning device against the edge of the hole of the workpiece;
Have
In the processing step, the shape of the hole of the workpiece is processed by the processing means in a state where the workpiece is immersed in a processing liquid,
In the air cleaning step, the air flow was blown from the air cleaning device to the edge portion of the hole of the workpiece drawn out from the inside of the processing liquid, so that the air flow adhered to the edge portion. An electrical discharge machining method in which the machining fluid is removed,
The processing means is a wire electrode that processes the shape of the hole by a discharge pulse generated between the hole and the hole,
The wire electrode is provided movably in the horizontal direction penetrating the hole in the machining liquid,
The imaging means and the illuminating means are arranged outside the working fluid and so that a straight line connecting the imaging means and the illuminating means is parallel to the moving direction of the wire electrode,
The electric discharge machining method , wherein the workpiece is provided so as to be movable between a straight line connecting the imaging unit and the illumination unit and in the machining liquid . The electric discharge machining method according to claim 3 , wherein, in the light irradiation step, light is irradiated from the illumination unit located on the same straight line as the imaging unit and the hole .

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